The invention relates to an arrangement in a microwave oven that comprises an oven cavity bounded by a plurality of conductive walls, a reclosable oven door giving access to the oven cavity and a microwave source mounted external of the oven cavity for feeding microwave energy into the interior of the oven cavity.
Normally, the oven cavity is a rectangular parallelepiped that has a highly symmetrical shape. However, in certain types of microwave ovens the shape of the oven cavity must have a certain degree of unsymmetry for reasons of manufacturing. This applies for instance to ovens of the "single-wall" type, in which at least one cavity wall also forms a part of the outer envelope wall of the oven. At the front of such an oven, the wall common to cavity and outer envelope must be bent for producing an access section cooperating with the oven door to provide a microwave seal, and also for producing a front having a sufficient mechanical stability. In this bent wall portion, an elongated groove-shaped recess will be formed that has an open side facing the oven cavity and that leads to an unsymmetry of the microwave field in the oven cavity, which unsymmetry is attributable to the fact that such a recess will involve a discontinuity of the microwave field boundary constituted by the oven cavity wall. Such groove-shaped recesses will aggravate the object of achieving a good microwave field distribution and thereby a uniform heating of the load in the oven cavity, in particular because the geometry and the size of the load will vary.